Gaining control over the grafting geometry is critically important for any application of surface-supported single-molecule magnets (SMMs) in data storage, spintronics, and quantum information science. Here, tetrairon(III) SMMs with a propeller-like structure are functionalized with thioacetyl-terminated alkyl chains to promote chemisorption on gold surfaces from solution and to evaluate differences in adsorption geometry and magnetic properties as a function of chain length. The prepared monolayers are investigated using X-ray absorption techniques with linearly and circularly polarized light to extract geometrical and magnetic information, respectively. All derivatives remain intact and form partially oriented monolayers on the gold surface. A ligand-field analysis of the observed X-ray natural linear dichroism shows that the threefold molecular axis is invariably biased toward the surface normal, in agreement with ab initio calculations. This preferential orientation is most pronounced in monolayers of the shortest-chain derivative, which are further studied with an ultralow temperature X-ray magnetic circular dichroism setup operating down to 350 mK. The isothermal field sweeps with the magnetic field at normal incidence show an open hysteresis loop below 1 K, while measurements at different incidence angles prove the magnetic anisotropy of the monolayers.

The organization of single-molecule magnets (SMMs) on surfaces is a mainstream research path in molecular magnetism. Of special importance is the control of grafting geometry in chemisorbed monolayers on metal surfaces. We herein present the synthesis, solid-state structure, and magnetic characterization of propeller-like tetrairon(III) SMMs containing the shortest-reported tethering groups for gold surfaces. Functionalization of molecular structure is attained using 2-R-2-(hydroxymethyl)propane-1,3-diol tripodal proligands (H3LR). The R substituents comprise a monomethylene spacer and three different terminations known to act as stable precursors of S-Au bonds (R = CH2SCN, CH2SAc and CH2SSnBu). These chemical groups are shown to be chemically compatible with the tetrairon(III) core and to afford fully-functional SMMs in crystalline form and in fair to excellent yields.

Quantum spin in single molecule magnets Single-molecule magnets are molecular complexes with magnetic bistability that may be exploited in information storage applications. Recently it was shown that such a molecular magnetic memory effect is retained for Fe4 clusters when they are wired to a gold surface. Mannini et al . have now tailored the clusters so that they have a preferential orientation and form a self-assembled monolayer on the surface. As a result, it becomes possible to observe a striking effect of single-molecule magnets — quantum tunnelling of the magnetization, which shows up as steps in the magnetic hysteresis loop. This approach may be of use for the design of practical thin-film molecular spintronic devices.

We have measured quantum transport through an individual Fe(4) single-molecule magnet embedded in a three-terminal device geometry. The characteristic zero-field splittings of adjacent charge states and their magnetic field evolution are observed in inelastic tunneling spectroscopy. We demonstrate that the molecule retains its magnetic properties and, moreover, that the magnetic anisotropy is significantly enhanced by reversible electron addition/subtraction controlled with the gate voltage. Single-molecule magnetism can thus be electrically controlled.

Tunable single-molecule magnets: The spin-level landscape in a series of Fe(III) (4) single-molecule magnets with propeller-like structure was analyzed by means of high-frequency EPR spectroscopy. The zero-field splitting parameter D of the ground S=5 spin state correlates strongly with the pitch of the propeller gamma (see picture), and thus provides a simple link between molecular structure and magnetic behavior.We report three novel tetrairon(III) single-molecule magnets with formula [Fe(4)(L)(2)(dpm)(6)] (Hdpm=2,2,6,6-tetramethylheptane-3,5-dione), prepared by using pentaerythritol monoether ligands H(3)L=R'OCH(2)C(CH(2)OH)(3) with R'=allyl (1), (R,S)-2-methyl-1-butyl (2), and (S)-2-methyl-1-butyl (3), along with a new crystal phase of the complex containing H(3)L=11-(acetylthio)-2,2-bis(hydroxymethyl)- undecan-1-ol (4). High-frequency EPR (HF-EPR) spectra at low temperature were collected on powder samples in order to determine the zero-field splitting (zfs) parameters in the ground S=5 spin state. In 1-4 and in other eight isostructural compounds previously reported, a remarkable correlation is found between the axial zfs parameter D and the pitch gamma of the propeller-like structure. The relationship is directly demonstrated by 1, which features both structurally and magnetically inequivalent molecules in the crystal. The dynamics of magnetization has been investigated by ac susceptometry, and the results analyzed by master-matrix calculations. The large rhombicities of 2 and 3 were found to be responsible for the fast magnetic relaxation observed in the two compounds. However, complex 3 shows an additional faster relaxation mechanism which is unaccounted for by the set of spin Hamiltonian parameters determined by HF-EPR.

The ability of a tetranuclear iron(III) single-molecule magnet functionalized with thioacetyl-terminated ligands to form monolayers on gold has been investigated by a multitechnique approach based on STM, XPS and ToF-SIMS. We discuss in detail several aspects, which are relevant to the reported observation of a memory effect on the monolayer prepared from dichloromethane (Mannini et al., Nat. Mater., 2009, 8, 194). In particular we show that the adsorbate comprises intact surface-bound Fe4 clusters as opposed to microcrystals or multilayers. The influence of the solvent used for the self-assembly process on the morphology, composition and structure of the adsorbate is also studied for four different solvents (dichloromethane, n-hexane, toluene, 1,4-dioxane).

Molecular magnets are promising for their use as high-density memory devices. However, maintaining the molecules’ magnetic state when bonded to a substrate has been impossible. The discovery, in sophisticated experiments, that single magnetic molecules can indeed show magnetic hysteresis when wired to a gold surface opens the door to individually address magnetic molecules.

Tripods of general formula R’–O–CH2C(CH2OH)3 are excellent site-specific ligands for the preparation of functionalized Fe4 single-molecule magnets. Herein, we describe the synthesis and characterization of two novel complexes designed to bind graphene surfaces, in which the R group consists of an alkyl spacer –(CH2)n– (n=6 and 10) and a terminal pyrenyl moiety. The site-specific ligand substitution on [Fe4(OMe)6(dpm)6] (Hdpm=dipivaloylmethane) with the new tripods has been studied with 2H NMR on isotopically-enriched samples, revealing that, once formed, these clusters are stable in solution over long timescales. It was not possible to isolate the new compounds as crystalline solids, nevertheless they were chemically characterized by elemental analysis and 1H NMR. The presence of the pyrenyl ending groups prompted us to investigate the effect of metal complexation on fluorescence, and a full pyrene-to-iron cluster excitation energy transfer was observed. The analysis of the magnetic behaviour revealed an S=5 ground spin state with a negative zero-field splitting parameter D=−0.42cm−1.

Devices and desires: The self-assembly of single-molecule-magnet (SMM) carbon-nanotube (CNT) hybrids (see picture) in conditions compatible to the creation of electronic devices is described. The process is controlled at the single-molecule level, and the resulting CNT–field-effect transistors display single-SMM sensitivity at room temperature. Detailed facts of importance to specialist readers are published as "Supporting Information". Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Magnetic circular dichroism was employed to investigate the magnetic behavior of a single-molecule magnet of the Fe4 family embedded in two different polymeric matrices. The influence of the host polymer in the magnetic response was discussed, and it was show that the choice of polymer, as well as its preparation process may greatly influence the magnetic behavior of the guest magnet.

Monoethers of pentaerythritol, R′O–CH2C(CH2OH)3, are convenient site-specific ligands for the design and preparation of functionalized Fe4 single-molecule magnets. Herein, we describe the synthesis, crystal and molecular structure and magnetic properties of a novel Fe4 derivatives with R′ = phenyl, obtained by site-specific ligand substitution on [Fe4(OMe)6(dpm)6] (Hdpm = dipivaloylmethane). The compound, which has the lowest molecular symmetry among all Fe4 derivatives so far reported (C1), retains the same S = 5 ground spin state as the parent compound, but show an enhanced easy-axis anisotropy with D = −0.433(2) cm−1, E = 0.014(2) cm−1 and B40=+1.5(1)×10-5cm-1 (from high frequency and X-band EPR). The thermal-activation parameters for magnetic moment reversal are Ueff/kB = 15.7(2) K and τ0 = 3.5(5) × 10−8 s (from AC susceptometry). Micro-SQUID measurements on single crystals show that below about 0.2 K the spin dynamics is dominated by quantum tunneling within the MS = ±5 ground doublet. In spite of the low molecular symmetry, which is generally believed to enhance tunneling effects, the relaxation time in the purely quantum regime is as long as ∼2.5 × 104 s (∼7 h).

Chaetomellic anhydride A was efficiently attained in three steps, starting from 2,2-dichloropalmitic acid and 2-(3-chloro-2-propenylamino)pyridine. Atom transfer radical cyclisation selectively formed the cis-stereoisomer of the trichloropyrrolidin-2-one, which underwent a stereospecific functional rearrangement to form a substituted maleimide. The choice of 2-pyridyl, as ‘cyclisation auxiliary’ in the atom transfer radical cyclisation step, proved beneficial for hydrolysis of the maleimide to form the desired anhydride.

The rearrangement of a trichloro-pyrrolidin-2-one, prepared by the CuCl–TMEDA catalyzed atom transfer radical cyclization of N-alkyl-N-(3-chloro-2-propenyl)-2,2-dichloromyristamide, with n-propylamine or CH3ONa/CH3OH, is the key step of a new, short and inexpensive route to chaetomellic anhydride C and (±)-erythro-roccellic acid.

The reaction of 4-methyl-pyrrolidin-2-ones, chlorinated at the C(3) and C(6) positions, with n-propylamine constitutes a new method for the preparation of 5-propylimino-pyrrolidin-2-ones or 3-pyrrolin-2-ones in generally good yields. The transformation involves a series of eliminations, substitutions and double bond shifts. This constitutes a remarkable example of a functional rearrangement.

A new chiral derivatizing agent for ee determination of 1,2-diols via (1)H NMR is described. (S)-(+)-N-acetylphenylglycineboronic acid (1) is synthesized in enantiomerically pure form; its reaction with chiral diols quantitatively yields cyclic boronic esters 5a-g. The latter show a remarkably high diastereodifferentiation of proton NMR signals useful for de determination. [reaction: see text]